The present invention relates to a surface acoustic wave device such as a resonator, a filter and so forth that is housed in a mobile communication apparatus such as a mobile telephone and so forth. More particular, the present invention relates to a package structure and a manufacturing method of the surface acoustic wave device.
Conventionally, for the surface acoustic wave device, a ceramic package for surface mounting, and a metal package by cold weld or electro-deposition have been employed.
FIG. 11 is a view illustrating a section of the surface acoustic wave device using the conventional ceramic package.
As shown in this Fig., in general, for the ceramic package is employed a multi-layer structure of a first ceramic layer 118, a second ceramic layer 119, and a third ceramic layer 120.
Further, in order to cover a top portion thereof with a cap 122, a metal ring 121 was brazed.
In such a multi-layer ceramic package, it is necessary to electrically connect a chip 101 comprising a piezoelectric substrate such as a crystal and so forth, and an external terminal 114 that is a pad for surface mounting.
Namely, a wire or a through hole is provided for a part of each ceramic layer, and a connection of the chip 101 to the external terminal 114 is made by taking a route from a bonding pad 117 mounted on the top side of the second ceramic layer 119 to an internal wiring 115.
The chip 101 is fastened to and mounted on the part of the first ceramic layer 118 with an adhesive 102 wherein metal plating 116 was formed.
Wiring of the chip 101 and the bonding pad 117 is carried out with a bonding wire 104.
Thereafter, the cap 122 is laid on the metal ring 121, a hollow section 105 is provided over the top face of the chip 101, and sealing is carried out with seam welding and so forth.
As to the sealing method, there is also the method of employing solder, gold-tin and so forth in addition to the seam welding.
In the surface acoustic wave device using the above-mentioned ceramic package, however a first problem exists that low pricing is difficult.
Namely, this is because, in the surface acoustic wave device using the ceramic package, since routing of the internal wiring becomes necessary and the multi-layer of the ceramic is required, a die for manufacturing becomes necessary every time the wiring layout is changed.
Also, this is because, as to the sealing method, in the case of the seam welding, it is necessary to braze the metal ring 121 on the ceramic, and also in the case of the solder sealing, it is unavoidable to prepare a special solder lid.
As the other conventional examples, the examples using the resin package were disclosed in JP-A-63495/1993 and JP-A-188672/1994.
In JP-A-63495/1993, was illustrated the example of a resin-mold peripheral unit having a hollow section on the top face of the surface acoustic wave element fastened to the lead frame, and, in this example, a conducting layer was provided in the internal surface thereof or a conductive resin was employed for the peripheral unit and it was illustrated that a lead wire was covered with an insulating film to wire it to an external terminal through the peripheral unit.
In this manner, the conductive layer of the internal surface of the peripheral unit or the conductive resin of the peripheral unit allows electrostatic coupling capacity between input and output of the surface acoustic wave elements to be dispersed and reduced and the attenuation volume of the surface acoustic wave device to be increased in the attenuation band.
Also, in JP-A-188672/1994 was illustrated the example of fitting the resin base, into which the lead frame was pre-molded, and a cap, which protects the surface of the chip mounted on the lead frame in midair, to bond the fitted fringe with resin.
Also, either of the devices illustrated in JP-A63495/1993 and JP-A-188672/1994, has a SIP (Single In-line Package) structure.
In the surface acoustic wave device disclosed in JP-A63495/1993, however, a third problem exists: it is necessary to cover with an insulating film from the inside of the device the periphery of the peripheral unit of which the internal surface is a conductive layer, or of the lead wire that is caused to pass through the peripheral unit that is formed of the conductive resin, whereby the production process increases and low pricing of the surface acoustic wave device is difficult.
Further, in the SIP-shape surface acoustic wave device disclosed in JP-A-63495/1993 and JP-A-188672/1994, a fourth problem exists: This is inclined when mounted on a printed circuit board, stress such as distortion of the printed circuit board and so forth has an influence over characteristics of the surface acoustic wave device, or unification of the surface-mounting surface acoustic wave device using the conventional ceramic package and the printed circuit board is impossible, whereby the specific printed circuit board becomes necessary.
Namely, this is because, in the above-mentioned surface acoustic wave device of which the structure is SIP-shaped, pins concentrates at one side.
Further, in the SIP-shape surface acoustic wave device disclosed in JP-A-63495/1993 and JP-A-188672/1994, in order to support the chip comprising the piezoelectric substrate, it was illustrated that it was fastened to and mounted on the lead frame; however a fifth problem exists that it is not suitable for downsizing.
Namely, this is because, since the lead frame for mounting the chip has much area than the area of the chip, the outer dimension of the surface acoustic wave device gets constrained by the area of the said lead frame for mounting the chip.